Fix FeatureStore list_entity_types() and EntityType list_features() #1684

Environment details

• OS type and version:
• Python version: 3.7.12
• pip version: 22.2.2
• google-cloud-aiplatform version: 1.16.1

Steps to reproduce

I was trying to list the the EntityTypes and the Features created in a FeatureStore from Vertex AI Workbench (I've already detailed the Environment details). The region I built the FeatureStore into is europe-west4, son when I try to list the entities and the features it keeps failing (more details in the Stack Trace and Code Example).

Code example

PROJECT_ID = "my-project"
REGION = "europe-west4"
FEATURESTORE_ID = "my_feature_store_id"

fs = FeaturestoreCustom(
    featurestore_name=FEATURESTORE_ID,
    project=PROJECT_ID,
    location=REGION,
)

fs.list_entity_types() # It fails here


entity_type = fs.get_entity_type(entity_type_id="my_entity_type_id")
entity_type.list_features() # It also fails here

Stack trace

InvalidArgument: 400 List of found errors:	1.Field: parent; Message: The provided location ID doesn't match the endpoint. The valid location ID is `us-central1`.	 [field_violations {
  field: "parent"
  description: "The provided location ID doesn\'t match the endpoint. The valid location ID is `us-central1`."
}
]

I'm going to drop a PR to solve this issue.

Thanks in advance!!